Biodegradation of Trichloroethylene and Dichloromethane in Contaminated Soil and Groundwater

Soil column and serum bottle microcosm experiments were conducted to investigate the potential for in situ anaerobic bioremediation of trichloroethy lene (TCE) and dichloromethane (DCM) at the Pinellas site near Largo, Florida. Soil columns with continuous groundwater recycle were used to evaluate treatment with complex nutrients (casamino acids, methanol, lactate, sulfate); benzoate and sulfate; and methanol. The complex nutrients drove microbial dechlorination of TCE to ethene, whereas the benzoate/sulfate and methanol supported microbial dechlorination of TCE only to cis-1 ,2-dichloroethylene (cDCE). Microbial sulfate depletion in the benzoate/sulfate column allowed further dechlorination of cDCE to vinyl chloride. Serum bottle microcosms were used to investigate TCE dechlorination and DCM biodegradation in Pinellas soil slurries bioaugmented with liquid from the soil columns possessing TCE-dechlorinating activity and DCM biodegradation by indigenous microorganisms. Bioaugmented soil microcosms showed immediate TCE dechlorination in the microcosms with methanol or complex nutrients, but no dechlorination in the benzoate/sulfate microcosm. DCM biodegradation by indigenous microorganisms occurred in soil microcosms amended with either benzoate/sulfate or methanol, but not with complex nutrients. Bioaugmentation stimulated DCM biodegradation in both complex nutrient and methanol-amended microcosms, but appeared to inhibit DCM biodegradation in benzoate/sulfate-amended microcosms. TCE dechlorination occurred before DCM biodegradation in bioaugmented microcosms when both compounds were present.     

Biodegradation of gasoline by gellan gum-encapsulated bacterial cells

Encapsulated cell bioaugmentation is a novel alternative solution to in situ bioremediation of contaminated aquifers. This study was conducted to evaluate the feasibility of such a remediation strategy based on the performance of encapsulated cells in the biodegradation of gasoline, a major groundwater contaminant. An enriched bacterial consortium, isolated from a gasoline-polluted site, was encapsulated in gellan gum microbeads (16-53 microm diameter). The capacity of the encapsulated cells to degrade gasoline under aerobic conditions was evaluated in comparison with free (non-encapsulated) cells. Encapsulated cells (2.6 mg(cells) x g(-1) bead) degraded over 90% gasoline hydrocarbons (initial concentration 50-600 mg x L(-1)) within 5-10 days at 10 degrees C. Equivalent levels of free cells removed comparable amounts of gasoline (initial concentration 50-400 mg x L(-1)) within the same period but required up to 30 days to degrade the highest level of gasoline tested (600 mg x L(-1)). Free cells exhibited a lag phase in biodegradation, which increased from 1 to 5 days with an increase in gasoline concentration (200-600 x mg L(-1)). Encapsulation provided cells with a protective barrier against toxic hydrocarbons, eliminating the adaptation period required by free cells. The reduction of encapsulated cell mass loading from 2.6 to 1.0 mg(cells) x g(-1) bead caused a substantial decrease in the extent of biodegradation within a 30-day incubation period. Encapsulated cells dispersed within the porous soil matrix of saturated soil microcosms demonstrated a reduced performance in the removal of gasoline (initial concentrations of 400 and 600 mg x L(-1)), removing 30-50% gasoline hydrocarbons compared to 40-60% by free cells within 21 days of incubation. The results of this study suggest that gellan gum-encapsulated bacterial cells have the potential to be used for biodegradation of gasoline hydrocarbons in aqueous systems.     

降解吡啶复合菌系MD1的筛选、降解特性及代谢途径

【目的】为筛选吡啶高效降解复合菌系,促进高浓度吡啶废水的降解。本研究围绕吡啶降解复合菌系的筛选、降解特性及代谢途径,旨在获得吡啶高效降解复合菌系,为高浓度吡啶废水微生物降解及完全矿化提供理论依据和技术支撑。【方法】以吡啶为唯一碳氮源从某农药废水处理系统好氧活性污泥中筛选得到一个吡啶高效降解复合菌系MD1。采用16S rRNA高通量测序技术探究了MD1的群落结构及多样性,通过单因素实验考察了MD1的降解特性,利用气相色谱-质谱联用仪对MD1降解吡啶的代谢产物进行了初步检测与鉴定,推测吡啶可能的降解途径。【结果】结果显示,在温度30 ℃、pH 8.0、NaCl浓度0.1%的最佳条件下培养72 h,MD1对初始浓度1 400 mg/L的吡啶降解率为98.44%±0.27%。在属水平上,MD1主要由副球菌属(Paracoccus sp.)、布鲁氏菌属(unclassified_Brucellaceae)、无色杆菌属(Achromobacter sp.)等组成。由代谢产物检测结果初步推测MD1对吡啶的代谢途径为吡啶→烟酸→6-羟基烟酸→2,5-二羟基吡啶→N-甲酰基马来酰胺酸→马来酰胺酸→马来酸→CO₂+H₂O。【结论】研究筛选得到一个可高效降解吡啶、降解性能稳定的复合菌系MD1。解析了MD1的微生物组成多样性和群落结构,推测了MD1可能的代谢途径,研究结果丰富了吡啶降解微生物资源。     

Dichloromethane utilized by an anaerobic mixed culture: acetogenesis and methanogenesis

Dichloromethane (8.9 mg/l) was eliminated from industrially polluted, anaerobic groundwater in a fixed-bed reactor (43 m³) which was packed with activated charcoal and operated continuously for over three years. The elimination of dichloromethane over this period was some ten-fold in excess of the sorptive capacity of the charcoal, and the elimination (3.7 mg/h·[kg of charcoal]: residence time, 49 h) was tentatively attributed to dehalogenative microorganisms immobilized on the charcoal. Anaerobic enrichment cultures, with dichloromethane as the sole added source of carbon and energy, were inoculated with material from the reactor. Reproducibly complete substrate disappearance in subcultures was observed when traces of groundwater (1%) or yeast extract (0.01%) were supplied. Fed-batch experiments under an atmosphere of CO₂ plus N₂ led to the conversion in 11 days of 11 mM dichloromethane to 3 mM acetate and 2 mM methane, with a growth yield of 0.4 g of protein/mol of dichloromethane; insignificant amounts (<1 M) of chloromethane accumulated. Methanogenesis could be inhibited by 50 mM 2-bromoethane sulfonate without any effect on the dehalogenation rate. The maximum dehalogenation rate was 0.13 mmol dichloromethane/h·l (2.6 mkat/kg of protein).Abbreviation DCM dichloromethane     

Phenanthrene Biodegradation in Soils Using an Antarctic Bacterial Consortium

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in Antarctic soils is limited by low temperatures, lack of adequate levels of nutrients, low number of PAH-tolerant members in the autochthonous microbiota and low bioavailability of contaminants. In the present work, microcosms systems (performed in 1-L glass flasks containing Antarctic soil supplemented with 1744 ppm of phenanthrene) were used to study (i) the effect of biostimulation with a complex organic source of nutrients (fish meal) combined with a surfactant (Brij 700); (ii) the effect of bioaugmentation with a psychrotolerant PAH-degrading bacterial consortium (M10); (iii) the effect of the combination of both strategies. The authors found that combination of biostimulation and bioaugmentation caused a significant removal (46.6%) of phenanthrene after 56 days under Antarctic environmental conditions. When bioaugmentation or biostimulation were applied separately, nonsignificant reduction in phenanthrene concentration was observed. Microtox test showed a low increase in toxicity only in the most efficient system. Results proved that “in situ” bioremediation process of phenanthrene-contaminated soils is possible in Antarctic stations. In addition, inoculation with a psychrotolerant PAH-degrading bacterial consortium in association with a mix of fish meal and a high-molecular-weight surfactant improved phenanthrene removal and should be the selected strategy when the number of hydrocarbons degrading bacteria in the target soil is low.     

邻苯二甲酸二(2-乙基己基)酯(DEHP)的细菌生物降解

邻苯二甲酸二(2-乙基己基)酯(dis(2-ethylhexyl)phthalate, DEHP)是一种人工合成的有机化合物,其作为增塑剂,因具有优良的柔韧性、可塑性和耐久性等特征而被广泛应用在个人护理、医疗器械、食品包装和塑料制造等领域。DEHP在土壤、水体和大气等环境中普遍存在,且由于DEHP是一种常见的内分泌干扰物,具有生殖毒性、免疫毒性以及神经毒性等,不仅给生态环境造成了威胁,而且可通过食物链进入人体给健康带来危害。因此,去除环境中的DEHP备受关注。DEHP的生物降解被认为是最绿色环保的降解方式,目前已有不少关于DEHP生物降解的研究报道。本文综述了DEHP的污染及危害、细菌生物降解现状,重点介绍了DEHP经酯键水解、β氧化、原儿茶酸降解、苯甲酸降解以及三羧酸循环等过程实现完全降解的途径,以及从基因层面阐述DEHP降解的分子机制,并针对DEHP生物降解目前还存在的问题进行总结和展望,为环境中DEHP有效生物降解提供参考。     

Phenol Biodegradation and Metal Removal by a Mixed Bacterial Consortium

This paper reports the tolerance and biodegradation of phenol by a heavy metal–adapted environmental bacterial consortium, known as consortium culture (CC). At the highest tolerable phenol concentration of 1200 mg/L, CC displayed specific growth rate of 0.04 h^?1, phenol degradation rate of 6.11 mg L^?1 h^?1 and biomass of 8.45 ± 0.35 (log₁₀ colony-forming units [CFU]/ml) at the end of incubation. Phenol was degraded via the ortho-cleavage pathway catalyzed by cathechol-1,2-dioxygenase with specific activity of 0.083 (µmol min^?1 mg^?1 protein). The different constituent bacterial isolates of CC preferentially grow on benzene, toluene, xylene, ethylbenzene, cresol, and catechol, suggesting a synergistic mechanism involved in the degradation process. Microtox assay showed that phenol degradation was achieved without producing toxic dead-end metabolites. Moreover, lead (Pb) and cadmium (Cd) at the highest tested concentration of 1.0 and 0.1 mg/L, respectively, did not inhibit phenol degradation by CC. Simultaneous metal removal during phenol degradation was achieved using CC. These findings confirmed the dual function of CC to degrade phenol and to remove heavy metals from a mixed-pollutant medium.     

Biodegradation and sorption properties of polydisperse acrylate polymers

Polyacrylate (PA), which is widely used in disposable diapers, is synthesized by polymerization and cross-linking of acrylate. During the synthesis, 3–6% of the polyacrylate polymers is not incorporated into the absorbent material, but remains soluble. If the soluble PA is mobilized from a landfill, it could enter the groundwater. Therefore, the biodegradation and adsorption properties of soluble polymers contained in PA are determined in this study. The soluble PA is highly polydisperse, and the fraction tested has a weight-average molecular-weight of 16,700 and a range extending from 10³ to 10⁵. Sand-column tracer tests show that about 1% of the polyacrylate is unadsorbed, but the remainder has a retardation factor that averages at least 58. Biodegradation kinetics are determined in completely mixed biofilm reactors having a methanogenic consortium grown on glucose. The polyacrylate fraction, as well as glucose and acrylate, are removed and mineralized to CO₂. The Monod parameters for the polyacrylate are: maximum specific rate of substrate utilization = 0.0016 gC/g biomass-day, and half-maximum-rate concentration = 0.79 gC/m³. Although these kinetics are much slower than for glucose and acrylate, significant degradation and mineralization are observed.     

Evaluation of Succession in an Estuarine Macrobenthic Soft-Bottom Community near Tampa,Florida

A subtidal macrobenthic infaunal community was quantitatively sampled monthly from February 1975 to July 1978 (42 months). During that period, complete defaunation (presumably due to hypoxia) occurred three times at approximately annual intervals. The recovery of the community was examined for successional patterns by quantitative and qualitative normal and inverse classification analyses and by rank-order analysis of the dominant species. There was no consistent pattern of succession from recovery to recovery. Samples taken just after defaunation were not similar to each other and no consistent suites of species were detected. Classical succession in which suites of species are successively replaced by other suites until a persisting suite of species occurs (faciliation model) was not found. Other models of succession are discussed.     

Macrobenthic Distribution within the Sediment along an Estuarine Salinity Gradient

The distribution of the macrobenthic infaunal community within the upper 25 cm of the sediment was studied at 16 stations in the lower Chesapeake Bay. Stations were located from the tidal freshwater to the polyhaline zone of major tributaries (James, York and Rappahannock Rivers) and in the polyhaline portion of the lower bay mainstem. Profiles for total number of individuals, total ash-free dry weight biomass and species encountered with depth were calculated. Except for the deep dwelling bivalve, Macoma balthica, tributary macrobenthic communities had a shallow depth distribution compared to the mainstem sites which were found in generally coarser sediments in the higher salinity region of the estuary.     

Enhanced Biodegradation of Casablanca Crude Oil by A Microbial Consortium in Presence of a Rhamnolipid Produced by Pseudomonas Aeruginosa AT10

The biodegradation of oil products in the environment is often limited by their low water solubility and dissolution rate. Rhamnolipids produced by Pseudomonas aeruginosa AT10 were investigated for their potential to enhance bioavailability and hence the biodegradation of crude oil by a microbial consortium in liquid medium. The characterization of the rhamnolipids produced by strain AT10 showed the effectiveness of emulsification of complex mixtures. The addition of rhamnolipids accelerates the biodegradation of total petroleum hydrocarbons from 32% to 61% at 10 days of incubation. Nevertheless, the enhancement of biosurfactant addition was more noticeable in the case of the group of isoprenoids from the aliphatic fraction and the alkylated polycyclic aromatic hydrocarbons (PHAS) from the aromatic fraction. The biodegradation of some targeted isoprenoids increased from 16% to 70% and for some alkylated PAHs from 9% to 44%.     

Norovirus Distribution within an Estuarine Environment

Human norovirus (NoV) has been studied extensively as an important cause of gastroenteritis outbreaks worldwide. While oysters are a primary vehicle for infection, few studies have examined the wider distribution of NoV in the estuarine environment. Active shellfish-harvesting areas in Georgia were examined for the prevalence, genotype diversity, and concentrations of NoV in a variety of estuarine sample types over the course of 1 year. Of the 225 samples (9 oyster, 72 water, 72 63- to 200-μm plankton, and 72 >200-μm plankton) collected from 12 stations across two estuaries, 21 samples (9.3%) tested positive for NoV. By sample type, 55.0% (5/9) of oysters, 8.3% (6/72) of water samples, 11.1% (8/72) of 63- to 200-μm plankton samples, and 2.8% (2/72) of >200-μm plankton samples were positive for human NoV. The two NoV-positive >200-μm plankton samples, which contained mainly zooplankton, had the greatest quantity of NoV genomes (3.5 × 10¹³ and 1.7 × 10¹⁵ genomes g⁻¹) of any sample tested. The majority, 90.5% (19/21), of the samples tested positive for genogroup I NoV, and only 9.5% (2/21) of the samples tested positive for genogroup II. The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human NoV in the water environment.Human norovirus (NoV) is the leading cause of nonbacterial gastroenteritis worldwide (3). The Centers for Disease Control and Prevention (CDC) estimate that 23 million cases of acute gastroenteritis due to NoV occur each year, with symptoms including acute-onset vomiting, watery nonbloody diarrhea with abdominal cramps, and nausea (35). NoV outbreaks are pervasive for many reasons, but particularly because the virus is highly contagious and environmentally hardy (7). Additionally, infected individuals can excrete millions of viral particles in feces, leading to large numbers in sewage (16). Without proper removal or inactivation during wastewater treatment, the viruses can be released into recreational and shellfish-harvesting water bodies. Complete inactivation of NoV during sewage treatment is rare, and even in areas with proper wastewater treatment, contamination of oyster beds has been reported (5, 16, 17, 32, 38). Because bivalve molluscan shellfish are believed to act as filters for viruses and other microbes and because NoV is extremely infectious (as little as one viral particle is required for disease), the disease risk for consumption of raw oysters is high (27, 33, 40).Human NoV genogroup I (GI) and GII have been detected in oyster samples harvested from bays and estuaries worldwide (5, 10, 20). Ueki et al. (42) detected NoV in both shellfish and the surrounding river water in Japan and concluded that NoV contamination was most likely due to sewage and treated wastewater input into the river; however, no study has yet been able to characterize how NoV may be naturally distributed in an estuarine system, including in water, adhered to particles (including plankton), and in shellfish. The limitations are due in part to a lack of adequate detection methods specifically adapted to different environmental-sample types (8). Using a newly developed detection and quantification protocol (21), this study aimed to examine the distribution of NoV genogroups across a range of sample types within an estuarine system with the goal of better characterizing possible circulation of viruses between water, plankton, and oysters.     

Electron-Microscopic Studies of the Colonies of an Alkylsulfonate-utilizing Bacterial Consortium

The light- and electron-microscopic analysis of the colonies of a bacterial consortium capable of utilizing alkylsulfonates, which are the main ingredients of waste from the synthetic rubber industry, revealed the presence of eight types of cells. All types of cells were gram-negative and differed in shape, size, and the presence of capsule and cytoplasmic inclusions. Three types of cells were present in all the colonies studied. The presence of the other types of cells depended on the inoculum used and on the composition of the growth medium.     

The Fractionation of Chlorine Isotopes by the Aerobic Methylotrophic Bacterium Methylobacterium dichloromethanicum Grown on Dichloromethane

Methylobacterium dichloromethanicum was found to be able to utilize dichloromethane (DCM) as the source of carbon and energy with the production of biomass, CO₂, and HCl. A comparative analysis of the abundances of the major DCM isotopomers ³⁵Cl₂ ¹²C¹H₂, ³⁵Cl³⁷Cl¹²C¹H₂, and ³⁷Cl₂ ¹²CH₂1H₂ made it possible to estimate the fractionation of chlorine isotopes during the bacterial metabolism of DCM. The kinetic chlorine isotope effects for ³⁵Cl³⁷Cl¹²C¹H₂ (m/z 86) and ³⁷Cl₂ ¹²C¹H₂ (m/z 88) relative to ³⁵Cl₂ ¹²C¹H₂ (m/z 84) were characterized by _86/84 = 1.006 ± 0.002 and _88/84 = 1.023 ± 0.003, respectively. The inference is made that the growth of M. dichloromethanicum on DCM is accompanied by the mass-independent fractionation of the DCM isotopomers.     

Biological decomposition of dichloromethane from a chemical process effluent

The application of specialized microorganisms to treat dichloromethane (DM) containing process effluents was studied. An aerobic fluidized bed reactor with a working volume of 801 filled with sand particles as carriers for the bacteria was used. Oxygen was introduced into the recycle stream by an injector device. DM was monitored semi-continuously. A processor controlled the feed volume according to the DM effluent concentration. Mineralization rates of 12 kg DM/m_bioreactor ³ · d were reached within about three weeks using synthetic wastewater containing 2000 mg/l DM as single carbon compound. DM from process water of a pharmaceutical plant was reduced from about 2000 mg/l in the feed to below 1 mg/l in the effluent at volumetric loading rates of 3 to 4 kg DM/m_bioreactor ³ · d. Degradation of wastewater components like acetone and isopropanol were favoured, thus making the process less attractive for waste streams containing high amounts of DOC other than of DM. DM concentrations of up to 1000 mg/l were tolerated by the immobilized microorganisms and did not influence their DM degradation capacity. The ability to mineralize DM was lost when no DM was fed to the reactor for 10 days.     

Persistence and Biodegradation of Spilled Residual Fuel on an Estuarine Beach

The enrichment of hydrocarbon-degrading bacteria and the persistence of petroleum hydrocarbons on an estuarine beach after a spill of residual fuel oil on 11 April 1973 in Upper Narragansett Bay, R.I. was investigated. A rapid enrichment occurred during days 4 to 16 after the oil spill and a significant population of hydrocarbon-degrading bacteria was maintained in the beach sand for at least a year. The concentration of petroleum hydrocarbons in the mid-tide area declined rapidly during the bacterial enrichment period, remained fairly constant throughout the summer, and then declined to a low concentration after 1 year. An increased concentration of branched and cyclic aliphatic hydrocarbons in the low-tide sediment 128 days after the spill suggested a migration of hydrocarbons during the summer. Hydrocarbon biodegradation was apparent during the winter months at a rate of less than 1 mug of hydrocarbon per g of dry sediment per day.     

生物降解萘的研究进展*

萘的生物降解具有低成本,效果佳,无二次污染等优势,受到全世界的广泛关注。本文从萘降解菌的种类、降解质粒与降解基因的开发与研究、三种降解途径的发展以及表面活性剂、菌体固定化技术和有机溶剂在萘降解和环境污染治理当中的应用情况等方面综述了生物降解萘的发展历程。从降解菌株的研究和表面活性剂以及生物技术手段的应用情况等角度分析了目前生物降解萘还存在的问题,并为解决这些问题提出了合理的方案。论述了两相体系技术在生物降解萘上的可应性,对其强大的发展潜力进行了展望。     

Dichloromethane as the sole carbon source forHyphomicrobium sp. strain DM2 under denitrification conditions

Hyphomicrobium sp. strain DM2 was found to grow anaerobically in the presence of nitrate with methanol, formaldehyde, formate or dichloromethane. The estimated growth rate constants with methanol and dichloromethane under denitrification conditions were 0.04 h^–1 and 0.015 h^–1, respectively, which is twofold and fourfold lower than the rates of aerobic growth with these substrates. Slight accumulation of nitrite was observed in all cultures grown anaerobically with nitrate. Dichloromethane dehalogenase, the key enzyme in the utilization of this carbon source, was induced under denitrification conditions to the same specific activity level as under aerobic conditions. In a fed batch culture under denitrification conditionsHyphomicrobium sp. DM2 cumulatively degraded 35 mM dichloromethane within 24 days. This corresponds to a volumetric degradation rate of 5 mg dichloromethane/l·h and demonstrates that denitrificative degradation offers an attractive possibility for the development of anaerobic treatment systems to remove dichloromethane from contaminated groundwater.     

硝化细菌群的富集及其去除城镇寡营养河道中氨氮污染的应用

[背景]随着工农业的发展,污水排放导致的氨氮超标逐渐成为水体污染的重要因素,脱氮已成为人们研究的重点.目前脱氮方法主要集中于硝化细菌的硝化作用,其将氨氮转化为硝酸盐氮,从而减少水体中氨氮的污染.由于工业废水和农业污水中的有机物含量较高,而且异养硝化细菌具有生长较快等优势,因此对异养菌的研究多于自养菌.然而现有的异养硝化...